scholarly journals Observation of sublimation of ice using terahertz spectroscopy

2020 ◽  
Vol 7 (9) ◽  
pp. 192083
Author(s):  
Keisuke Matsumura ◽  
Kodo Kawase ◽  
Kei Takeya
Keyword(s):  
Absorption Coefficient ◽  
Phase Change ◽  
Time Scale ◽  
Terahertz Spectroscopy ◽  
Entire Temperature Range ◽  
Thz Spectroscopy ◽  
Interesting Phenomenon ◽  
Temperature Range ◽  
Ice Sublimation

Although many studies have investigated the phase change of water, few have focused on the sublimation of ice. This study revealed that ice sublimation can be observed using terahertz (THz) spectroscopy. From measurements in the range of 210–270 K, the sublimation was observed over the entire temperature range and the rate of sublimation was increased proportionally with temperature. Particularly on a time scale of a few hundred minutes, the sublimation progresses visibly above 250 K. Above a certain temperature, the absorption coefficient increased during sublimation. These findings suggest that an interesting phenomenon may occur in the phase change of water at sub-zero temperatures, indicating that THz spectroscopy would be useful for measuring water and ice.

scholarly journals Temperature dependent poly(L-lactide) crystallization investigated by Fourier transform terahertz spectroscopy

2021 ◽  
Author(s):  
Seiichiro Ariyoshi ◽  
Satoshi Ohnishi ◽  
Hikaru Mikami ◽  
Hideto Tsuji ◽  
Yuki Arakawa ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Absorption Spectra ◽  
Terahertz Spectroscopy ◽  
Thz Spectroscopy ◽  
Frequency Range ◽  
Temperature Dependent ◽  
Thz Absorption

Poly(L-lactide) (PLLA) was investigated by Fourier transform terahertz (THz) spectroscopy over the frequency range of 1.0 – 8.5 THz. THz absorption spectra were acquired for PLLA samples isothermally crystallized at...

scholarly journals Experimental Study on Flow Characters of Salt Hydrate Slurry in Phase Change Temperature Range

2017 ◽  
Vol 21 (5) ◽  
pp. 15-23
Author(s):  
Muhammad Irsyad ◽  
Yuli S. Indartono ◽  
Ari D. Pasek ◽  
Willy Adriansyah
Keyword(s):  
Experimental Study ◽  
Phase Change ◽  
Salt Hydrate ◽  
Phase Change Temperature ◽  
Temperature Range ◽  
Change Temperature

scholarly journals Rayleigh–Bénard convection in a creeping solid with melting and freezing at either or both its horizontal boundaries

2018 ◽  
Vol 846 ◽  
pp. 5-36 ◽  
Author(s):  
Stéphane Labrosse ◽  
Adrien Morison ◽  
Renaud Deguen ◽  
Thierry Alboussière
Keyword(s):  
Boundary Condition ◽  
Rayleigh Number ◽  
Phase Change ◽  
Time Scale ◽  
Critical Rayleigh Number ◽  
Classical Case ◽  
Bénard Convection ◽  
Benard Convection ◽  
Rayleigh Benard Convection ◽  
Rayleigh Benard

Solid-state convection can take place in the rocky or icy mantles of planetary objects, and these mantles can be surrounded above or below or both by molten layers of similar composition. A flow towards the interface can proceed through it by changing phase. This behaviour is modelled by a boundary condition taking into account the competition between viscous stress in the solid, which builds topography of the interface with a time scale $\unicode[STIX]{x1D70F}_{\unicode[STIX]{x1D702}}$, and convective transfer of the latent heat in the liquid from places of the boundary where freezing occurs to places of melting, which acts to erase topography, with a time scale $\unicode[STIX]{x1D70F}_{\unicode[STIX]{x1D719}}$. The ratio $\unicode[STIX]{x1D6F7}=\unicode[STIX]{x1D70F}_{\unicode[STIX]{x1D719}}/\unicode[STIX]{x1D70F}_{\unicode[STIX]{x1D702}}$ controls whether the boundary condition is the classical non-penetrative one ($\unicode[STIX]{x1D6F7}\rightarrow \infty$) or allows for a finite flow through the boundary (small $\unicode[STIX]{x1D6F7}$). We study Rayleigh–Bénard convection in a plane layer subject to this boundary condition at either or both its boundaries using linear and weakly nonlinear analyses. When both boundaries are phase-change interfaces with equal values of $\unicode[STIX]{x1D6F7}$, a non-deforming translation mode is possible with a critical Rayleigh number equal to $24\unicode[STIX]{x1D6F7}$. At small values of $\unicode[STIX]{x1D6F7}$, this mode competes with a weakly deforming mode having a slightly lower critical Rayleigh number and a very long wavelength, $\unicode[STIX]{x1D706}_{c}\sim 8\sqrt{2}\unicode[STIX]{x03C0}/3\sqrt{\unicode[STIX]{x1D6F7}}$. Both modes lead to very efficient heat transfer, as expressed by the relationship between the Nusselt and Rayleigh numbers. When only one boundary is subject to a phase-change condition, the critical Rayleigh number is $\mathit{Ra}_{c}=153$ and the critical wavelength is $\unicode[STIX]{x1D706}_{c}=5$. The Nusselt number increases approximately two times faster with the Rayleigh number than in the classical case with non-penetrative conditions, and the average temperature diverges from $1/2$ when the Rayleigh number is increased, towards larger values when the bottom boundary is a phase-change interface.

The Metal-Dielectric Transition in Short-Pulse Laser Ablation of Metals

Volume 4 ◽  
2004 ◽  
Author(s):  
Cristian Porneala ◽  
David A. Willis
Keyword(s):  
Laser Ablation ◽  
Absorption Coefficient ◽  
Phase Change ◽  
Pulse Laser ◽  
Pulse Laser Ablation ◽  
Short Pulse ◽  
Phase Explosion ◽  
Short Pulse Laser ◽  
Dielectric Transition

Phase explosion is an explosive liquid-vapor phase change that occurs during short pulse laser ablation. Phase explosion results from homogenous vapor nucleation in a superheated liquid phase as the surface temperature approaches the thermodynamic critical temperature, Tc. For a metastable liquid, the upper limit of superheating is approximately 0.9Tc, above which the rate of homogeneous nucleation rises dramatically. Prior to reaching the superheat limit however, a “dielectric transition” is expected to occur at approximately 0.8Tc. The dielectric transition is the transition of an electrically conductive material to a non-conducting state due to large fluctuations in material properties. One consequence of the dielectric transition is that the material will become semi-transparent. Until now, little work has been performed to understand the role of the dielectric transition in laser ablation, and many questions remain about how the surface will rise above 0.8Tc if the surface is semitransparent and only weakly absorbing. This work investigates the role of the dielectric transition with a one-dimensional numerical model for heat transfer and phase change and includes the effect of the metal to dielectric transition. The model is used to simulate heating of aluminum by a Nd:YAG laser with a 7 nanosecond pulse width (FWHM) at the fundamental wavelength of 1064 nm. Calculations of the transient temperature field, melt depth, and depth of the dielectric layer are obtained. Estimates of the absorption coefficient of a metal surface above the metal-dielectric transition are made from correlations found in the research literature. The value of the absorption coefficient is shown to be a critical parameter for determining the energy density required to reach 0.9Tc.

High-Precision Continuous-Wave Terahertz Spectroscopy Based on a Photomixing Technique for Identifying Pearls

2019 ◽  
Vol 73 (12) ◽  
pp. 1388-1393
Author(s):  
Chihoon Kim ◽  
Taeksoo Ji
Keyword(s):  
Optical Coherence Tomography ◽  
Fourier Transform ◽  
Ir Spectroscopy ◽  
Continuous Wave ◽  
Terahertz Spectroscopy ◽  
Thz Spectroscopy ◽  
Ft Ir ◽  
Thz Absorption ◽  
Ft Ir Spectroscopy ◽  
Cultured Pearls

We present the accurate terahertz spectra of between imitation and cultured pearls using continuous-wave terahertz (CW-THz) spectroscopy. Using Fourier transform infrared (FT-IR) spectroscopy and optical coherence tomography (OCT) measurements, cultured pearls can be distinguished from imitation pearls by observing distinct absorption peaks and discriminative boundaries. The THz absorption spectra up to 0.3 THz obtained from CW-THz spectroscopy show several absorption peaks at specific frequencies with the cultured pearls but no peaks with the imitation pearls, which results from the existence of the nacre polymorph of cultured pearls. Hence, it is expected that the CW-THz system proposed herein will be applicable to fast, nondestructive spectrum analysis including pearl identification.

scholarly journals Hot-salt corrosion of alloys PT-7M, 42ХНМ, Inconel 690, Incoloy 800

2019 ◽  
Vol 121 ◽  
pp. 04015
Author(s):  
Oleg Bykh ◽  
Aleksandr Bakhmetev ◽  
Natin Sandler ◽  
Petr Tryaev ◽  
Anna Ershova ◽  
...  
Keyword(s):  
Corrosion Behavior ◽  
Entire Temperature Range ◽  
Water Steam ◽  
Testing Conditions ◽  
Temperature Range ◽  
Saturated Water ◽  
Salt Corrosion ◽  
Inconel 690 ◽  
Incoloy 800

The Article contains the results of the study performed for the samples made from alloys PT-7М, 42ХНМ, Inconel 690, Incoloy 800 for resistance against hot salt corrosion in the mixture of crystallized NaCl and KBr salts, in ratio 300:1 by weight, and in the temperature range from 150 °С to 300 °С, both in contact with the air and in a leak-tight autoclave in the atmosphere of saturated water steam. Regularities of hot salt corrosion behavior in the alloys under the study were detected under testing conditions. The atmosphere of saturated water steam inhibits development of halt salt corrosion of alloy ПТ-7М in the entire temperature range of the testing.

scholarly journals Terahertz Spectroscopy of Gas Absorption Using the Superconducting Flux-Flow Oscillator as an Active Source and the Superconducting Integrated Receiver

Sensors ◽  
2020 ◽  
Vol 20 (24) ◽  
pp. 7267
Author(s):  
Nickolay V. Kinev ◽  
Kirill I. Rudakov ◽  
Lyudmila V. Filippenko ◽  
Andrey M. Baryshev ◽  
Valery P. Koshelets
Keyword(s):  
Open Space ◽  
Terahertz Spectroscopy ◽  
Near Field ◽  
Gas Absorption ◽  
Thz Spectroscopy ◽  
Single Chip ◽  
Flux Flow ◽  
Practical Applications ◽  
Active Source ◽  
Integrated Receiver

We report on the first implementation of a terahertz (THz) source based on a Josephson flux-flow oscillator (FFO) that radiates to open space. The excellent performance of this source and its maturity for practical applications has been demonstrated by the spectroscopy of gas absorption. To study the radiated power, we used a bolometric detection method and additionally calibrated the power by means of pumping the superconductor–insulator–superconductor (SIS) junction, integrated on a single chip with the FFO. For calibration, we developed a program using the SIS-detected power calculations in accordance with the Tien and Gordon model. The power emitted to open space is estimated to be from fractions of µW to several µW in the wide region from 0.25 THz up to 0.75 THz for different designs, with a maximum power of 3.3 µW at 0.34 THz. Next, we used a gas cell and a heterodyne superconducting integrated receiver to trace the absorption lines of water and ammonia with a spectral resolution better than 100 kHz. Our experiment for gas absorption is the first demonstration of the applicability of the FFO as an external active source for different tasks, such as THz spectroscopy, near-field THz imaging and microscopy.

Normal and Anomalous Yield Stresses in a Tial Single Crystal and the Dominating Dislocation Mechanisms.

1994 ◽  
Vol 364 ◽  
Author(s):  
N. Bird ◽  
G. Taylor ◽  
Y. Q. Sun
Keyword(s):  
Single Crystal ◽  
Yield Stress ◽  
Slip Plane ◽  
Cross Slip ◽  
Axial Orientation ◽  
Entire Temperature Range ◽  
Temperature Range

AbstractSingle crystal γ-TiAl with axial orientation [3 16 15] has been tested in compression between 4K and 1048K and the dislocation structures observed in TEM. The slip plane was found to be (111) over the entire temperature range tested. Three regimes exist in the variation of the yield stress with temperature, whereas the dislocation substructures are of two types, dominated by 30° 1/3[112] and 1/2 < 110] dislocations respectively. The anomalous yield stress is associated with 1/2 < 110] dislocations undergoing frequent cross-slip off the (111) plane.

Sign in / Sign up

Export Citation Format

Share Document